Direct air capture of carbon dioxide

Abstract

A system for direct air capture (DAC) of carbon dioxide uses a liquid CO2-absorbent solvent that enables the hybridization of a cooling tower with CO2 DAC systems. A liquid solvent such as monoethanolamine (MEA) is added to cooling water to absorb CO2 from ambient air, the cooling water is used for its original purpose, and CO2 is recovered from the cooling water in a novel process. Initially, this combination of CO2 absorbent and cooling water would appear to be undesirable, since liquid CO2 solvents such as MEA are hygroscopic, and cooling towers reject heat via evaporation. However, an absorbent concentration range was identified where CO2 could be still absorbed and water evaporated, and a novel process for absorbent solvent regeneration was created.

What is claimed is: 
     
         1 . A system for direct air capture (DAC) of CO 2 , comprising:
 (a) a contactor bed comprising an upstream side and a downstream side;   (b) an air mover;   (c) whereby the air mover causes air to be passed through the contactor bed in an airflow from the upstream side to the downstream side;   (d) a solvent retention system disposed on the downstream side of the contactor bed;   (e) whereby air sequentially flows initially through the contactor bed and then through the solvent retention system;   (f) a coolant transported to the contactor bed;   (g) the coolant comprising:
 (i) substantially water; and 
 (ii) a liquid carbon dioxide solvent; 
   (h) whereby the liquid carbon dioxide solvent captures carbon dioxide from the airflow that passes through the contactor bed;   (i) whereby makeup water supplied to the solvent retention system substantially retains liquid carbon dioxide solvent as solvent laden makeup water;   (j) a catchment basin disposed beneath the contactor bed and the solvent retention system;   (k) whereby the coolant and solvent laden makeup water falls to the catchment basin as a cooled solution.   
     
     
         2 . The system of  claim 1 , wherein a concentration of the liquid carbon dioxide solvent in the coolant is about 1% to 5% by weight, or about 3%. 
     
     
         3 . The system of  claim 1 , wherein as the coolant flows through the cooling tower:
 (a) a temperature of the coolant decreases to form the cooled solution; and   (b) the liquid carbon dioxide solvent absorbs carbon dioxide to increase a carbon dioxide concentration of the solvent.   
     
     
         4 . The system of  claim 1 , wherein the liquid carbon dioxide solvent comprises an amine. 
     
     
         5 . The system of  claim 4 , wherein the liquid carbon dioxide solvent is substantially monoethanolamine (MEA). 
     
     
         6 . The system of  claim 4 , wherein the liquid carbon dioxide solvent is a liquid carbon dioxide solvent selected from a group monoethanolamine (MEA), methyldiethanolamine (MDEA), diethanolamine (DEA), 2-amino-2-methyl-1-propanol (AMP), and mixtures thereof. 
     
     
         7 . The system of  claim 4 , wherein the liquid carbon dioxide solvent further comprises an activator. 
     
     
         8 . The system of  claim 7 , wherein the activator is piperazine or 1-Dimethylamino-2-propanol. 
     
     
         9 . The system of  claim 1 , wherein the cooling tower comprises a bilevel injection system, and wherein when in operation, the coolant is transported to the contactor bed, and substantially solvent-free water is transported to the solvent retention system. 
     
     
         10 . The system of  claim 1 , wherein the cooling tower airflow configuration is selected from: crossflow, counterflow, and a combination of crossflow and counterflow. 
     
     
         11 . A system for direct air capture (DAC) of CO 2 , comprising:
 (a) a contactor bed comprising an upstream side and a downstream side;   (b) an air mover;   (c) whereby the air mover causes air to be passed through the contactor bed in an airflow from the upstream side to the downstream side;   (d) a solvent retention system disposed on the downstream side of the contactor bed;   (e) whereby air sequentially flows initially through the contactor bed and then through the solvent retention system;   (f) a coolant supply in fluid connection with the contactor bed;   (g) a water supply in fluid connection with the solvent retention system.   
     
     
         12 . The system of  claim 11 , wherein the coolant comprises:
 (a) substantially water; and   (b) a liquid carbon dioxide solvent.   
     
     
         13 . The system of  claim 12 ,
 (a) wherein the liquid carbon dioxide solvent captures carbon dioxide from the airflow that passes through the contactor bed;   (b) wherein makeup water supplied to the solvent retention system substantially retains liquid carbon dioxide solvent as solvent laden makeup water.   
     
     
         14 . The system of  claim 13 , further comprising:
 (a) a catchment basin disposed beneath the contactor bed and the solvent retention system;   (b) whereby the coolant and solvent laden makeup water falls to the catchment basin as a cooled solution.   
     
     
         15 . A method of direct air capture (DAC) of CO 2 , comprising the steps of:
 (a) moving air comprising a component of carbon dioxide sequentially through:
 (i) a contactor bed comprising an upstream side and a downstream side; and then 
 (ii) a solvent retention system disposed on the downstream side of the contactor bed; 
   (b) transporting a coolant to the contactor bed;   (c) the coolant comprising:
 (i) substantially water; and 
 (ii) a liquid carbon dioxide solvent; 
   (d) capturing carbon dioxide from the air that passes through the contactor bed by direct air capture with the liquid carbon dioxide solvent;   (e) whereby makeup water supplied to the solvent retention system substantially retains liquid carbon dioxide solvent as solvent laden makeup water;   (f) providing a catchment basin disposed beneath the contactor bed and the solvent retention system;   (g) whereby the coolant and solvent laden makeup water falls to the catchment basin as a cooled solution; and   (h) providing an air mover that moves the moving air.   
     
     
         16 . The method of  claim 15 , wherein a concentration of the liquid carbon dioxide solvent in the coolant is about 1% to 10% by weight, or about 3%. 
     
     
         17 . The method of  claim 16 , wherein as the coolant flows through the cooling tower:
 (a) a temperature of the coolant decreases to form the cooled solution; and   (b) the liquid carbon dioxide solvent absorbs carbon dioxide to increase a carbon dioxide concentration of the solvent.   
     
     
         18 . The method of  claim 17 , wherein the liquid carbon dioxide solvent is substantially monoethanolamine (MEA). 
     
     
         19 . The method of  claim 18 , wherein the liquid carbon dioxide solvent is a liquid carbon dioxide solvent selected from a group monoethanolamine (MEA), methyldiethanolamine (MDEA), diethanolamine (DEA), 2-amino-2-methyl-1-propanol (AMP), and mixtures thereof. 
     
     
         20 . The method of  claim 19 , wherein the liquid carbon dioxide solvent further comprises an activator comprising: piperazine or 1-Dimethylamino-2-propanol.